If took clindamycin before w/no problem does that mean safe to take it again or is every time like the first time?

Antibiotic use: No medication are innocuous, each one have its possible secondary effects or harmful effects, thats the cause that they only are prescribed for an expert (your doctor). Always important to finish the entire cycle (days of medication prescribed) to prevent bacterial resistance to antibiotics. If you are referring to allergy kind of effect - every substance could generate an allergy effect.